U.S. patent number 4,222,929 [Application Number 06/032,049] was granted by the patent office on 1980-09-16 for low-shrink in-mold coating.
This patent grant is currently assigned to The General Tire & Rubber Company. Invention is credited to Donald F. Reichenbach, Henry Shanoski.
United States Patent |
4,222,929 |
Shanoski , et al. |
September 16, 1980 |
Low-shrink in-mold coating
Abstract
A laminate comprises an adherent in-mold thermoset coating
composition on a thermoset polyester glass fiber substrate, the
coating composition comprising essentially the reaction product of
an unsaturated aliphatic fumarate polyester diol, a saturated
polyester diol flexibilizer, a cross-linking aliphatic polyol
having from 3 to 6 OH groups, a diisocyanate in an amount by weight
sufficient to provide from about 50 to 120%, preferably from about
80 to 99%, of the stoichiometric amount of --NCO groups required to
react with all of the active hydrogen atoms in the coating
composition and an ethylenically unsaturated monomer sufficient to
polymerize with and crosslink the unsaturated polyester in
admixture with a minor amount by weight of polyvinyl acetate which
serves to reduce or eliminate shrinkage of the coating
composition.
Inventors: |
Shanoski; Henry (Akron, OH),
Reichenbach; Donald F. (Massillon, OH) |
Assignee: |
The General Tire & Rubber
Company (Akron, OH)
|
Family
ID: |
21862825 |
Appl.
No.: |
06/032,049 |
Filed: |
April 23, 1979 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
958771 |
Nov 8, 1978 |
4189517 |
Feb 19, 1980 |
|
|
Current U.S.
Class: |
523/514; 525/126;
525/131; 523/521; 525/127 |
Current CPC
Class: |
C08G
18/68 (20130101); C08K 3/013 (20180101); C09D
175/14 (20130101); C08L 67/06 (20130101); C08L
75/06 (20130101); C08L 67/02 (20130101); C08L
31/04 (20130101); C08K 3/36 (20130101); C08K
3/22 (20130101); C08K 3/26 (20130101); C08K
3/34 (20130101); C08L 67/06 (20130101); C09D
175/14 (20130101); C08L 2666/02 (20130101); C08L
2666/04 (20130101); C08L 2666/54 (20130101) |
Current International
Class: |
C08L
67/06 (20060101); C08G 18/68 (20060101); C09D
175/14 (20060101); C08G 18/00 (20060101); C08L
67/00 (20060101); C08K 003/22 (); C08K 003/26 ();
C08K 003/34 (); C08K 003/36 () |
Field of
Search: |
;260/4TN
;525/126,127,131 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Person; Sandra M.
Parent Case Text
This is a division of application Ser. No. 958,771 filed Nov. 8,
1978 now U.S. Pat. No. 4,189,517, issued Feb. 19, 1980.
Claims
We claim:
1. A thermosetting composition comprising essentially:
(a) an unsaturated aliphatic polyester fumarate diol having an
average molecular weight of from about 1,500 to 4,500 and from
about 8 to 30 internal aliphatic carbon-to-carbon double bonds,
(b) a saturated aliphatic polyester diol flexibilizer having an
average molecular weight of from about 1,500 to 3,000, (b) being
present in a minor molar amount as compared to (a),
(c) an aliphatic crosslinking polyol having from 3 to 6 hydroxyl
groups and an average molecular weight of from about 92 to
1,000,
(d) a diisocyanate selected from the group consisting of
2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenyl
methane diisocyanate, 4,4'-dicyclohexyl methane diisocyanate,
polymeric forms of TDI, MDI and hydrogenated MDI, xylene
diisocyanate, isophorone diisocyanate and hexamethylene
diisocyanate and mixtures thereof, said diisocyanate being present
in an amount by weight sufficient to provide from about 50 to 120%
of the stoichiometric amount of --NCO groups required to react with
all of the active hydrogen atoms in said composition, and
(e) an ethylenically unsaturated monomer selected from the group
consisting of styrene, alpha methyl styrene, vinyl toluene, methyl
methacrylate, acrylamide, acrylonitrile, methyl acrylate and
mixtures thereof, said monomer being present in an amount
sufficient to copolymerize with and crosslink said unsaturated
polyester, in admixture with
(f) from about 2 to 20 parts by weight of polyvinyl acetate per 100
parts by weight of said total composition.
2. A composition according to claim 1 in which said diisocyanate is
present in an amount by weight sufficient to provide from about 80
to 99% of the stoichiometric amount of --NCO groups required to
react with all of the active hydrogen atoms in said
composition.
3. A composition according to claim 1 containing additionally a
filler selected from the group consisting of clay, talc, MgO,
Mg(OH).sub.2, CaCO.sub.3 and silica and mixtures thereof.
4. A composition according to claim 1 in which in said composition
(a) is a copolymer obtained from maleic anhydride and propylene
oxide, (b) is polyethylene butylene adipate, (c) is the adduct of
propylene oxide and pentaerythritol having an average molecular
weight of from about 400 to 600, (d) is 4,4'-diphenylmethane
diisocyanate, (e) is styrene and the polyvinyl acetate of (f) is
present in an amount of from about 3 to 13 parts by weight per 100
parts by weight total of said coating composition.
5. A composition according to claim 4 in which said composition
contains additionally talc and/or CaCO.sub.3.
6. A composition according to claim 4 in which (d) is a
diisocyanate terminated polyurethane prepolymer containing excess
diisocyanate made by reacting the diisocyanate of (d) with at least
a portion of (c).
Description
This invention relates to a low-shrink thermoset in-mold coating
composition containing a minor amount by weight of polyvinyl
acetate.
BACKGROUND
A major deficiency of compression molded thermoset (cured) glass
fiber reinforced polyester (FRP) moldings is surface imperfections
such as pits, pores, surface cracks, waviness and sink marks
requiring substantial post-curing handling such as sanding, filling
and so forth requiring considerable expense in additional materials
and labor. The in-mold coating process of U.S. Pat. No. 4,081,578
masks these imperfections by molding a low viscosity thermosetting
composition onto the surface of the thermoset FRP part in a second
molding operation. The resulting skin or thin adherent thermoset
coating, however, experiences about an 8% volume shrinkage on
curing although pits, pores, cracks, waviness and sink marks are
generally eliminated. In the case of pits slight dimples in the
coating at those locations sometimes remain. The shrinkage is due
to polymerization and/or crosslinking and also due to thermal
effects caused by cooling.
It is an object of the present invention to avoid the difficulties
alluded to hereinabove and to provide an in-mold coating
thermosetting composition which exhibits a reduced amount of or no
shrinkage on molding and curing.
Another object of the present invention is to provide a thermoset
polyester glass fiber reinforced part with an in-mold molded
adherent thermoset coating which exhibits a reduced amount of or no
shrinkage.
These and other objects and advantages of the present invention
will become more apparent to those skilled in the art from the
following detailed description and working examples.
DISCUSSION OF THE PRIOR ART
In copending U.S. Patent Application of Sigurdur I. Arnason, Ser.
No. 814,502, filed July 11, 1977 there is disclosed an in-mold
coating composition comprising a vinyl ester of the reaction
product of acrylic acid and the diglycidyl ether of bisphenol A in
styrene, CaCO.sub.3, peroxide catalyst, inhibitor, mold release
agent and polyvinyl acetate (40% PVA in STY monomer) as the low
shrink additive. Additional styrene and other fillers can be used.
While polyvinyl acetate is preferred, it is stated that copolymers
of vinyl acetate such as the acidic copolymers and rubber or
thermoplastic homopolymers and copolymers of butadiene such as
copolymers of butadiene and styrene or acrylonitrile as well as
polymethyl methacrylate, polyethylene and polystyrene, also, may be
used as low shrink additives. Moreover, the ester resin may be
replaced in part by other unsaturated polyester resins made from
glycols and unsaturated dicarboxylic acids as well as those made
from propylene oxide and maleic anhydride. Copending U.S. Patent
Application of Sigurdur I. Arnason, Ser. No. 897,980, filed Apr.
20, 1978 (as a continuation-in-part of Ser. No. 814,502, above) has
a similar disclosure and additionally discloses the use of a
silicate filler having a sheet-like structure such as talc and mica
and states that viscosity can be increased by using clay. Neither
one of these applications discloses any data on shrinkage nor the
use of any isocyanates or polyisocyanates.
U.S. Pat. No. 3,741,799 in column 3, lines 56-62, discloses that
the polyester resin used in FRP molding compositions can be
rendered low-shrink or low-profile by adding finely divided
particles of thermoplastic resins like polymethyl methacrylate,
polypropylene, polyethylene, high-impact polystyrene, etc., in
solution with a cross-linkable monomer like styrene. It does not
disclose polyvinyl acetate. It refers to Australian Patent
Application No. 24,802/67 (based on U.S. Ser. No. 566,580 filed
July 20, 1966; see U.S. Pat. No. 3,772,241 below). It has nothing
to do with in-mold coating but is concerned with paint adhesion to
an FRP part.
U.S. Pat. No. 3,772,241 discloses in column 4, lines 31-45, that in
the FRP composition the thermosetting polymer can be, for example,
homopolymers of methyl methacrylate, ethyl methacrylate, butyl
methacrylate, methyl acrylate, ethyl acrylate, styrene, copolymers
of methyl methacrylate and lower alkyl esters of acrylic and
methacrylate acids, and copolymers of methyl methacrylate with
minor amounts of one or more of the following: lauroyl
methacrylate, isobornyl methacrylate, acrylamide, hydroxyethyl
methacrylate, styrene, 2-ethylhexyl acrylate, acrylonitrile,
methacrylic acid, methacrylamide, methylol acrylamide, and cetyl
stearyl methacrylate. Other useful examples of the thermoplastic
polymer are styrene/acrylonitrile copolymers, vinyl chloride/vinyl
acetate copolymers, cellulose acetate butyrate, and cellulose
acetate propionate. The reference has nothing to do with in-mold
coating and does not disclose polyvinyl acetate per se.
U.S. Pat. No. 3,883,612 discloses the preparation of a maleic
anhydride-propylene glycol polyester partial prepolymer which is
then reacted with dicyclopentadiene to make a dicyclopentadiene
terminated polyester. Next there is reacted more propylene glycol
with the DCPD partial polyester prepolymer. To this composition is
added an unsaturated monomer like styrene and a functional
thermoplastic polymer. The functional thermoplastic polymer is the
terpolymer resulting from the copolymerization of an unsaturated
ester like methyl methacrylate, an unsaturated acid like acrylic
acid and vinyl acetate. The terpolymer apparently prevents phase
separation between the styrene and polyester resin and also
promotes thickening with chemical thickeners (col. 4, lines 63-68,
and col. 6, lines 15-21). The composition is useful for molding
with glass fibers and fillers. The reference does not disclose
in-mold coating of an FRP part nor polyvinyl acetate.
German Offen. No. 2,448,929, laid-open Apr. 29, 1976, and English
translation thereof (corresponds to U.S. Pat. No. 4,051,085),
discloses a thermosetting composition useful for impregnating glass
fibers and comprising a copolymerizable vinyl compound like
styrene, a thermoplastic polymer, and an unsaturated polyester
polyurethane. Fillers etc. can be added. Among the large number of
thermoplastic polymers (m.w. 500-10,000,000, preferred m.w.
10,000-50,000; preferred m.w. 500-5,000 for polycondensates and
addition compounds) disclosed, there is suggested homopolymers,
copolymers and graft polymer of vinyl acetate. However, the
preferred thermoplastic polymers are those containing acid groups
and the cellulose esters such as cellulose acetoproprionate or
butyrate. The only polyester shown in the examples is one made from
maleic anhydride and propylene glycol having a molecular weight of
498, but it is stated that m.w. can be less than 1,240, preferably
370-930. The only polyester polyurethanes actually shown are in
Tables II and III where tolylene diisocyanate and the polyester or
polyester plus isopropyl alcohol are reacted in an equivalent ratio
(NCO/OH+COOH) of 1:2 or 1:2.17 which represents 50% or less than
50% of the stoichiometric amount of NCO required to react with all
of the active hydrogen atoms of the unsaturated polyester although
it is stated that the equivalent ratio of NCO to OH is 1:1 to 1:3,
preferably 1:1.5 to 1:2.5 (a NCO stoichiometry of 100 to 33%,
preferably 67% to 40%). The presence of COOH will produce CO.sub.2
and foaming. A flexibilizing low m.w. diol and an aliphatic low
m.w. cross-linking polyol having from 3-6 OH groups are not shown.
Depending on the pressures used Table VII, Runs 1-4, shows relative
shrinkages of 20-38% and 49-79%.
French Pat. No. 2,364,119 (published April, 1978), and English
translation thereof, discloses a sheet of polymethylmethacrylate
containing an adherent layer of a composition of a polyester resin,
styrene, polyvinylacetate (up to 10%) to improve adhesion, peroxide
catalyst, amine accelerator, up to 30% glass fibers, and as a
filler preferably CaSO.sub.4 (19-25 wt. %). It does not disclose
diisocyanates nor in-mold coating.
Union Carbide Corporation, "Bakelite" Low Profile Additives,
Bulletin No. F46567, 16 pages, no date, shows on page 3 the use of
LP-100 (40% polyvinyl acetate in styrene) in a
polyester-styrene-glass fiber composition (BMC formula) to get low
(0.3 mils/in.) shrinkage (about 4 parts by weight of PVA on 100 of
total components). On page 14, it discloses the use of LP-90 (40%
PVA in styrene) in a polyester-styrene-glass fiber premix
formulation (BMC formula) composition but does not give any
shrinkage data (about 3.9 parts PVA on 100 of total composition).
This reference does not disclose in-mold coating nor
diisocyanates.
SUMMARY OF THE INVENTION
According to the present invention there is provided a laminate
comprising an adherent in-mold thermoset coating composition
in-mold coated on a thermoset polyester glass fiber substrate, the
coating composition comprises essentially the reaction product of
an unsaturated aliphatic fumarate polyester diol, a saturated
polyester diol flexibilizer, a crosslinking aliphatic polyol having
3 to 6 OH groups, a diisocyanate in an amount by weight sufficient
to provide from about 50 to 120%, preferably from about 80 to 99%,
of the stoichiometric amount of --NCO groups required to react with
all of the active hydrogen atoms in the coating composition and an
ethylenically unsaturated monomer sufficient to polymerize with and
crosslink the unsaturated polyester in admixture with a minor
amount by weight of polyvinyl acetate which serves to reduce or
eliminate shrinkage of the coating composition.
The in-mold coating composition reduces the surface imperfections
as discussed above and additionally provides for reduced or no
shrinkage. The adhesion of the coating to the substrate can be very
high and the surface is smoother. It is not precisely known what
occurs, but it may be that during the thermosetting or curing of
the in-mold coating composition the polyvinyl acetate exists as a
separate phase and relieves the internal polymerization shrinkage
forces by creating minute internal voids in the coating structure
so that the bulk shrinkage of the coating remains at a minimum.
DISCUSSION OF DETAILS AND PREFERRED EMBODIMENTS
Polyvinyl acetate is a well known polymer and can be prepared by
bulk, solution, emulsion or dispersion polymerization processes
using free-radical catalysts. See Schildknecht, "Vinyl and Related
Polymers," John Wiley & Sons, Inc., New York, 1952, page 323 to
341; Schildknecht, "Polymer Processes," High Polymers, Vol. X,
Interscience Publishers, Inc., New York, 1956; Matthews, "Vinyl and
Allied Polymers," Vol. 2, Iliffe Books, London, 1972; and
"Encyclopedia of Polymer Science and Technology," Vol. 15, 1971,
Interscience Publishers a division of John Wiley & Sons, Inc.,
New York, pages 577 to 677. The polyvinyl acetate is used in an
amount of from about 2 to 20, preferably in an amount of from about
3 to 13, parts by weight per 100 parts by weight total of the
(in-mold) coating composition. If too little polyvinyl acetate is
used, the resulting coating evidences little improvement in
reduction in shrinkage. If too much polyvinyl acetate is employed,
the coating tends to be soft, cheesy and easily attacked by paint
solvents.
The unsaturated aliphatic polyester is made by copolymerizing
maleic anhydride and an alkylene oxide of 3 to 4 carbon atoms such
as propylene oxide, butylene oxide, isobutylene oxide and so forth
and mixture thereof. Propylene oxide is preferred. The alkylene
oxide should be used in a molar ratio greater than the maleic
anhydride to provide a polyester which is essentially or all OH
terminated, e.g., a polyester diol. The polyester should have an
average molecular weight of from about 1500 to 4500 and from about
8 to 30 internal aliphatic carbon-to-carbon double bonds. Up to
about 10 mol % of the maleic anhydride may be replaced with a
saturated anhydride such as phthalic anhydride or other anhydride
and mixture thereof as shown in U.S. Pat. No. 3,538,043. Also, up
to 10 mol % of the alkylene oxide moiety may be ethylene oxide;
greater amounts are undesirable since it may lead to water
sensitivity in the final product. These unsaturated polyesters are
made in benzene, styrene or other solvent using a double metal
cyanide catalyst as shown in U.S. Pat. No. 3,538,043. As shown in
said patent an isomerization catalyst such as piperidine is used to
isomerize the maleate double bonds of the polyester to fumarate
double bonds. Morpholine, also, may be used as an isomerization
catalyst as shown by U.S. Pat. No. 3,576,909.
Polyesters made by reacting maleic anhydride or maleic acid with a
glycol like propylene glycol, dipropylene glycol, 1,4-butane diol
and so forth may likewise be used, but such esterification
processes are time consuming and require high temperatures which
are expensive. Esters made by processes using catalysts like
titanium compounds are undesirable since it is difficult to remove
the titanium catalyst residues which can adversely accelerate the
isocyanate --OH condensation polymerization causing undesirable
reactions. Preferred are the polyesters made using the double metal
cyanide catalysts as described above.
A saturated aliphatic dihydroxy terminated polyester, also, is
employed in the in-mold coating composition to give some degree of
flexibility to the coating. It is used in a minor molar amount as
compared to the unsaturated polyester diol. The average molecular
weight of the saturated polyester is from about 1,500 to 3,000. It
can be made by methods well known to the art and should be free of
catalyst residues which would adversely affect the urethane forming
reaction. Examples of such polyesters are polyethylene butylene
adipate (preferred), polyethylene butylene sebacate, polypropylene
adipate, polybutylene suberate, polypropylene sebacate and the like
and mixture thereof.
The aliphatic polyol crosslinker used in the urethane reaction can
be glycerol, trimethylol propane, 1,2,6-hexane triol,
pentaerythritol, pentols, sorbitol and other aliphatic polyols
having from 3 to 6 hydroxyl groups and their propylene oxide,
butylene oxide and/or isobutylene oxide adducts (which may contain
up to 10 mol % ethylene oxide or be endcapped with ethylene oxide)
having an average molecular weight of from about 92 to 1,000.
Methods of making the alkylene oxide adducts of the polyols (except
glycerine) using a double metal cyanide catalyst are shown by U.S.
Pat. No. 3,829,505. Grafted polyols may, also, be used such as
those shown by U.S. Pat. Nos. 3,304,273; 3,383,351 and 3,294,711.
If the adducts or telomers are made using KOH or NaOH, the
resulting polyetherpolyol should be washed and/or neutralized to
reduce or remove the alkaline material which may adversely catalyze
the urethane reaction. The aliphatic polyol crosslinker is used in
an amount sufficient with the unsaturated polyester diol and any
other OH compound to provide adequate crosslinking with the
diisocyanate to provide a urethane network of sufficient crosslink
density to provide the desired hardness and toughness. The
propylene oxide adducts of pentaerythritol having an average
molecular weight of from about 400 to 600 are preferred.
The diisocyanate employed may be used as such or reacted with part
of the polyol to form a prepolymer, especially when hexamethylene
diisocyanate is employed since this isocyanate is believed to be
carcinogenic. The diisocyanate should be used in an amount by
weight sufficient to provide from about 50 to 120%, preferably from
about 80 to 99%, of the stoichiometric amount of --NCO groups
required to react with all of the active hydrogen atoms (as
determined by the Zerewitinoff method, J.A.C.S., Vol. 49, p. 3181
(1927) e.g., hydroxyl groups, of the polyester(s) and polyol(s) and
any other OH containing organic compound in the in-mold coating
compound taking into consideration the possibility of forming also
some biuret or allophanate linkages. Examples of useful
diisocyanates or mixtures thereof to employ are 2,4-tolylene
diisocyanate (TDI), 2,6-tolylene diisocyanate (TDI), 4,4'-diphenyl
methane diisocyanate (MDI), hydrogenated 4,4'-diphenyl methane
diisocyanate (or 4,4'-dicyclohexyl methane diisocyanate), polymeric
forms of TDI, MDI and hydrogenated MDI, xylene diisocyanate,
isophorone diisocyanate and hexamethylene diisocyanate. Of these
diisocyanates it is preferred to use 4,4'-diphenyl methane
diisocyanate.
The ethylenically unsaturated monomer used to crosslink the
unsaturated polyester diol and provide, together with the urethane
linkages, a thermoset coating is selected from the group consisting
of styrene, alpha methyl styrene, vinyl toluene, methyl
methacrylate, acrylamide, acrylonitrile, methyl acrylate and
mixtures of these. Of these monomers styrene is preferred. The
ethylenically unsaturated monomer is used in an amount sufficient
to copolymerize with and/or crosslink the unsaturated polyester
diol on being catalyzed by means of a free-radical catalyst to form
a crosslinked thermoset polyester resin coating.
A free-radical or free-radical generating catalyst such as a
peroxide is used to catalyze the copolymerization or crosslinking
between the ethylenically unsaturated low molecular weight monomer
and the unsaturated polyester. Examples of free-radical catalysts
include tertiary butyl perbenzoate, tertiary butyl peroctoate in
diallyl phthalate, diacetyl peroxide in dimethyl phthalate,
dibenzoyl peroxide, di(p-chlorobenzoyl) peroxide in dibutyl
phthalate, di(2,4-dichlorobenzoyl) peroxide with dibutyl phthalate,
dilauroyl peroxide, methyl ethyl ketone peroxide, cyclohexanone
peroxide in dibutyl phthalate,
3,5-dihydroxy-3,5-dimethyl-1,2-dioxacyclopentane, t-butyl peroxy
(2-ethyl hexanoate), 2,5-dimethyl-2,5-di(benzoyl peroxy) hexane,
t-butyl peroxy (2-ethyl butyrate), 2,5-dimethyl-2,5-bis(t-butyl
peroxy) hexane, cumyl hydroperoxide, diacetyl peroxide,
3,5-dihydroxy-3,5-dimethyl-1,2-oxacyclopentane, and 1,1-bis(t-butyl
peroxy)-3,3,5-trimethyl cyclohexane and the like and mixtures
thereof. It is desirable sometimes to use mixtures of peroxides to
take advantage of their different decomposition rates and times at
different temperatures and so forth. Preferred catalysts are
tertiary butyl perbenzoate and tertiary butyl peroctoate in diallyl
phthalate and mixtures thereof. For more information on peroxide
catalysts please see "Encyclopedia of Polymer Science and
Technology," Vol. 9, Interscience Publishers a division of John
Wiley & Sons, Inc., New York, 1968, pages 814 to 841.
The polyurethane catalyst, if employed since it is not always
needed, should be one which does not accelerate the decomposition
of the peroxide catalyst. The urethane catalyst when used should
facilitate readily the curing of the coating composition; that is,
the formation of the urethane network between the isocyanate and
active hydrogen containing compounds should proceed simultaneously
and smoothly along with the crosslinking operation caused by the
free-radical catalyst between the unsaturated monomer and the
unsaturated polyester. Examples of such catalysts are dibuytyl tin
dilaurate (preferred), dibutyl tin diacetate, tributyl tin acetate,
dilauryl tin diacetate, dibutyl tin di-2-ethyl hexoate, di-2-ethyl
hexyl tin bis(2-ethyl hexoate), dibutyl tin distearate, tetramethyl
tin and tetra-n-butyl tin and the like and mixtures thereof.
The free-radical catalysts and the polyurethane forming catalysts
are used in a minor amount sufficient to chain extend and
cross-link the functional components of the coating composition to
obtain a thermoset material.
The composition additionally can be filled or compounded to give
the desired viscosity and flow to the composition for molding and
to afford the desired physical properties to the resulting
thermoset coating. Examples of such fillers or compounding
ingredients are fillers like clay, talc, MgO, Mg(OH).sub.2,
CaCO.sub.3 and silica, mold release agents, red iron oxide,
TiO.sub.2, carbon black, organic color pigments like phthalocyanine
blue or green, antidegradants, U-V absorbers, calcium silicate,
hollow glass or resin micro-spheres, thickening agents, inhibitors
and the like. Preferred fillers are clay, talc, MgO, Mg(OH).sub.2,
CaCO.sub.3 and silica and mixtures thereof. These fillers and
compounding ingredients should be used in amounts sufficient to
provide satisfactory results. However, care should be exercised in
the use of high filler contents as this may give high viscosities
and result in flow and handling difficulties.
All of the ingredients of the in-mold coating composition should be
kept dry or have a minimal amount of moisture or the water content
should be controlled to obtain reproducible results, to avoid using
unnecessary amounts of isocyanates and to prevent foaming or pore
formation.
All of the ingredients of the in-mold coating composition can be
mixed together and then poured or injected onto the substrate and
molded and cured. Several streams or lines can be used to deliver
the components of the in-mold coating composition to a mixing head
or machine. However, since the mixed in-mold coating composition
has a limited shelf-life or storageability due to the reactivity of
the diisocyanate with the polyols, it is preferred to react the
diisocyanate with a portion of the polyol(s) to form an isocyanate
terminated prepolymer having excess free isocyanate. Moreover,
since the diisocyanate may be rather fluid, it is preferred for
handling purposes to increase its viscosity by forming the
isocyanate prepolymer. Mixing of the ingredients should be
thorough. A stream of the prepolymer and a stream containing the
unsaturated polyester composition of the desired viscosity are then
fed to the mixing head of a mixing machine which then delivers the
reactable in-mold coating to the surface of the substrate where it
is molded and cured to the substrate. Injection or compression,
transfer molding, or other molding apparatus or machines can be
used for the in-mold coating, and temperatures and times can be
those generally disclosed in U.S. Pat. No. 4,081,578, above.
Molding apparatus and methods for molding substances and in-mold
coating, also, may be found in U.S. Pat. Nos. 4,076,780; 4,076,788
and 4,082,486.
The processes and products of the present invention can be used in
the manufacture of automobile parts such as grille and headlamp
assemblies, deck hoods, fenders, door panels and roofs as well as
in the manufacture of food trays, applicance and electrical
components, furniture, machine covers and guards, bathroom
components, electronic part encapsulation, structural panels and so
forth. The fiberglass reinforced polyester (FRP) substrate can be a
sheet molding compound (SMC) or a bulk molding compound (BMC), wet
lay-up or other thermosetting FRP material as shown by "Modern
Plastics Encyclopedia," October, 1975, Vol. 52, No. 10A,
McGraw-Hill, Inc., New York, pages 105 to 107.
The following examples will serve to illustrate the present
invention with more particularity to those skilled in the art.
EXAMPLE I
Fiberglass polyester resin compositions were compression molded and
cured as plates according to the process of U.S. Pat. No. 4,081,578
to make a thermoset substrate. The composition used for the
substrate contained the following ingredients:
______________________________________ Ingredient Parts by Weight
______________________________________ "Paraplex" P340 4,000
"Paraplex" P681 2,240 "Paraplex" P543 772 "Camel-Wite" 10,520 TBP
70 Zinc stearate 350 Mg(OH).sub.2 316 Glass fibers 7,830
______________________________________
After cure, the thermoset substrate plates were furrowed or drilled
(as described below) and in-mold coated with several compositions
according to the process of U.S. Pat. No. 4,081,578 by mixing the
resin composition and the low shrink additive together and then
mixing therewith the isocyanate hardener composition. The resulting
mixture was then deposited on the outer surface of the compression
molded substrate and cured under heat and pressure. The ingredients
of the in-mold compositions were as follows:
______________________________________ Isocyanate (hardener)
Composition Ingredient Parts by Weight
______________________________________ "Isonate" 143L 16.7
"Pluracol" PeP 450 2.4 TBP .6 PDO solution .1 Resin Composition A
Ingredient Parts by Weight ______________________________________
Polyester 1050.6 Georgia Talc 450 748 "Formrez" L4-71 298
"Pluracol" PeP 450 163 "Zelec" UN 1.7 Benzoquinone solution 13.1
"Stan-Tone" 143 Resin Composition B ingredient Parts by Weight
______________________________________ Polyester 15 "Formrez" L4-71
4.35 "Pluracol" PeP 450 3.15 "Zelec" UN .025 Benzoquinone solution
.35 T-12 solution .10 Resin Composition C Ingredient Parts by
Weight ______________________________________ "Paraplex" P340 50
"Paraplex" P701 37.7 CaCO.sub.3 12.1 Zinc stearate 4.4 PDO solution
.5 TBP .5 "Marinco" H 3.9 Low Shrink Additive Composition
Ingredient Parts by Weight ______________________________________
LP-90, 40% polyvinyl acetate in styrene variable Other Additive
Ingredient Parts by Weight ______________________________________
Talc and/or CaCO.sub. 3 variable
______________________________________
The amounts of materials used and the results obtained are shown in
Table I below:
TABLE I
__________________________________________________________________________
Isocyanate Resin Hardner Resin Composition Composition LP-90 Talc
CaCO.sub.3 PPVA/H Run No. Composition Grams Grams Grams Grams Grams
Shrinkage Adhesion IMCC***
__________________________________________________________________________
1 C* -- -- -- -- -- Poor-Fair (M) Poor -- 2 C -- -- -- -- --
Excellent (M) Poor -- 3 C -- -- -- -- -- 0.22% (N) None -- 4 3 28
10 -- -- -- Poor (M) Poor -- 5 B 28 10 -- 12.75 -- Poor (M) Good/
-- Excellent 6 A 40.7 10 -- -- -- 8.6% (N) Good -- 7 B 28 10 10 --
-- Good (M) Poor 8.3 8 B 28 10 10 12.75 -- Good (M) Excellent 6.6 9
A 40.7 10 9.5 -- -- 2.1% (N) Good 6.3 10 B 28 10 10 -- 12.75 Good
(M) Good 6.6 11 A 40.7 10 19.3 -- -- 4.5% (N) Good 11. 12 B 28 10
20 12.75 -- Good/ Excellent 11. Excellent (M) 13 A 40.7 10 9.5 5.8
-- 2.2% (N) Good 5.7 14 A 40.7 10 19.3 10.5 -- 2.4% (N) Good 9.6 15
A 40.7 10 24.4 10.5 -- 3.1% (N) Good 11. 16 A 40.7 10 24.4 14.0 --
2.0% (N) Good 11. 17 A 40.7 10 24.4 10.5 4.7 2.5% (N) Weak 11. 18 A
40.7 10 9.5 -- 14 2.1% (N) Good 5.1 19 A 40.7 10 19.3 -- 24.4 1.4%
(N) Good 8.2 20 A 40.7 10 24.4 -- 31.4 1.7% (N) Good 9.2 21 B 28 10
25 -- 37.5 Excellent (M) Good 10. 22 A** 40.7 10 25.6 -- 58 0.73%
(N) No Data 7.5 23 B 28 10 25 -- 75 Excellent (M) Good 7.2
__________________________________________________________________________
*Minus CaCO.sub.3. **Plus 1.25 grams styrene. ***Parts by weight
polyvinyl acetate per se per 100 parts by weight of entire inmold
coating composition.
The adhesion test was done by cross hatching the coating with a
knife and attempting to peel-off the coating. The degree to which
the coating resisted peeling-off was a measure of its adhesion to
the thermoset polyester fiber glass substrate.
Two methods of coating shrinkage evaluation were used. In the first
method, see M above, after molding the 15".times.15" FRP plate, a
0.08".times..about.4" furrow was cut into the plate, and the
in-mold coating composition was hand-poured. After curing and
cooling the coated plate part, the shrinkage of the coating was
visually judged on the basis of how well it bridged the furrow; for
example, how much of a visible depression remained at the furrow
due to shrinkage of the coating (excellent =<1.5%, good=1.5-3%,
fair=3-4% and poor=>4% shrinkage). In the second method, see N
above, after curing the 15".times.15" FRP plate, the plate was
removed from the mold and a one-inch diameter hole was drilled
through it. The plate was then reseated in the mold and the in-mold
coating composition was hand-poured. After curing and cooling, the
thickness of the molded-in plug versus the adjacent FRP thickness
was a measure of the coating's shrinkage.
It is noted that while Runs 1 to 3 (without isocyanate, without
polyvinyl acetate) had poor-fair, 0.22% or excellent shrinkage, the
adhesion was unsatisfactory. Runs 4 to 6 (with isocyanate, without
polyvinyl acetate) had poor to excellent adhesion but the shrinkage
was unsatisfactory. Runs 7 to 23 showed good to excellent shrinkage
results with only one run showing a shrinkage greater than 4%.
Also, except in two instances the adhesion was good or
excellent.
EXAMPLE II
The method of this example was the same as that of Example I,
above. The same isocyanate (hardener) composition was used. The
resin composition was as follows:
______________________________________ Resin Composition D
Ingredient Parts by Weight ______________________________________
Polyester 1500 "Formrez" L4-71 435 "Pluracol" PeP 450 315 "Zelec"
UN 2.5 Benzoquinone solution 35 T-12 solution 10 Georgia Talc 650
1093 ______________________________________
The steps of mixing of the components of the in-mold composition,
coating the substrate FRP plate, compression molding and curing
were the same as those of Example I, above. The relative
proportions of the components of the in-mold coating composition
were as follows:
______________________________________ Component Parts by Weight
______________________________________ Isocyanate (hardener) 40.8
composition Resin Composition D 10 Low-shrink additive 20
composition ______________________________________
The results obtained on testing are shown in Table II, below:
______________________________________ Low-Shrink PLSH/H Run
Additive IMCC No. Composition Shrinkage ****
______________________________________ 31 "Paraplex" Poor (M) 9.9
P-543 32 "Paraplex" Poor (M) 9.9 P-701 33 "Formrex" L4-71 Poor (M)
9.9 35% by weight in styrene 34 "Microthene" Poor (M) 28 (PE) 35
7609 (SBR) Poor (M) 10.5 36 LP-40 Poor (M) 11 37 LP-60 Poor (M) 11
38 LP-90 Good (M) 11 39 LP-100 Fair to 11 Good (M)
______________________________________ ***Parts by weight of low
shrink additive per se per 100 parts by weight of entire inmold
coating composition.
The results of the runs of this example show that polyvinyl acetate
gives fair to good results as to shrinkage as compared to the poor
results exhibited by polymethyl methacrylate, acid modified
polymethyl methacrylate, polyethylene butylene adipate,
polyethylene, high styrene-butadiene copolymer, acid modified
polyvinyl acetate and acid modified polycaprolactone.
NOTES
Polyester--Polypropylene fumarate polyester, OH terminated, acid
No. of less than 1, average molecular weight of about 2,400, about
15 double bonds, in styrene monomer (70% by weight PE, 30% STY).
Prepared according to the teachings of U.S. Pat. No. 3,538,043 by
reacting propylene oxide and maleic anhydride initiated by fumaric
acid using a double metal cyanide catalyst and isomerized with
piperidine.
Georgia Talc 450 and 650, magnesium silicate (Soapstone).
"Formrez" L4-71--Ethylene butylene adipate polyester, about 2,000
m.w., saturated, OH terminated. Witco Chemical Company.
"Pluracol" PeP 450--Propylene oxide adduct of pentaerythritol,
average molecular weight about 450, equivalent hydroxyl weight of
101. BASF Wyandotte.
"Zelec" UN--Fatty alcohol phosphate, unneutralized. du Pont.
Benzoquinone--2% by weight benzoquinone in styrene.
T-12--1% by weight dibutyl tin dilaurate in styrene.
"Stan-Tone"--HLC No. 6543 pigment. Mixture of TiO.sub.2 and carbon
black in "Pluracol" PeP 450, 60% solids. Harwick Chemical Corp.
"Isonate" 143 L--Essentially diphenylmethane-4,4'-diisocyanate, a
liquid. The Upjohn Company.
TBP--Tertiary butyl perbenzoate.
PDO--Tertiary butyl peroctoate, 50% by weight in diallyl
phthalate.
"Paraplex" P 340--A 65% by weight solution of polyester in styrene,
the polyester being essentially a polypropylene fumarate, OH No. of
35, COOH No. of 35, average molecular weight of about 1,600. Rohm
& Haas Company.
"Marinco" H--Magnesium hydroxide, Merck & Co., Inc.
"Paraplex" P 681--35% by weight solution of polymethylmethacrylate
containing some carboxyl groups in styrene. Rohm & Haas
Company.
"Paraplex" P 543--35% by weight solution of polymethyl methacrylate
in styrene. Rohm & Haas Company.
"Paraplex" P 701--35% by weight solution of acid modified
polymethyl methacrylate in styrene. Rohm & Haas Company.
"Microthene"--Polyethylene, powdered. U.S. Industrial Chemical
Co.
7609--XD-7609. Copolymer of about 63% styrene and 37%
butadiene-1,3, may contain some homopolystyrene. 54.1% trans-1,4,
13.1% vinyl, Mn about 115,000.
About 37% solids in styrene. Dow Chemical Co.
"Bakelite" LP-40--40% by weight solution of acid modified polyvinyl
acetate in styrene. Union Carbide Corp.
"Bakelite" LP-60--40% by weight solution of acid modified
polycaprolactone in styrene. Union Carbide Corp.
"Bakelite" LP-90--40% by weight solution of polyvinyl acetate in
styrene, viscosity of 1,800 centipoises at 25.degree. C. (Model LVT
Brookfield viscometer # 4 spindle at 60 rpm), specific gravity
20/20.degree. C. (H.sub.2 O=1) of 1.008 and solidification
temperature of 5.degree. C. Union Carbide Corp.
"Bakelite" LP-100--40% by weight solution of polyvinyl acetate in
styrene. Viscosity of 5,000 centipoises, water content of 0.20
weight percent, and acid number of 3.0. Union Carbide Corp.
"Camel-Wite"--Calcium carbonate (limestone), average particle size
of 3.3 microns. Campbell Grove Division of H.M. Royal.
* * * * *